Catalytic cracking which came of age as a major refining process in 1940's was revitalized by the introduction of molecular sieve type catalyst. It was found that dramatic improvements in cracking activity and selectivity could be obtained by incorporating relatively small amounts of molecular sieves into the catalyst. The sieves were found to have intrinsic activities for cracking far greater than the conventional amorphous-silica-alumina catalyst.
There are several patents describing processes for preparation of these zeolites. U.S. Pat. No. 3,692,665, for example, covers a method of preparing a faujasite type zeolite that is stabilized by cation and thermal stabilization. The older and more conventional cracking catalysts are described in patents such as U.S. Pat. No. 3,404,097 to Wilson et al. which describes a silica magnesia flouride catalyst. U.S. Pat. No. 3,650,988 of Magee et al. covers a process for preparing a hydrocarbon conversion catalyst containing a semisynthetic portion, i.e., clay and silica alumina, and a zeolitic portion. There are several other patents describing processes for preparing molecular sieves containing catalysts. U.S. Pat. No. 3,425,956 of Baker et al. is typical of a large body of art in this area.
U.S. Pat. No. 3,753,929 of Linsey is typical of a body of art describing zeolite catalysts in a silica matrix wherein a silica sol is used to furnish the silica for the catalyst preparation. U.S. Pat. No. 3,499,846 to Michalko describes another process for preparing these catalysts. The processes described in the prior art are fairly complex and require both washing and exchange steps to remove the sodium.